Historically, optical fibers have been added to textile structures, laminates, or composites to take advantage of the functional attributes of these fibers, such as the ability to transmit light, and data encoded in the light, over extended distances. In addition, modifications to the fiber—such as mechanical notches in the coating and/or fiber, small radius bends in the fiber, or chemical modifications of the cladding or protective layers of the optical fiber—can result in light leakage from the fiber and a decreased light transmission. If the decreased light transmission is due to interaction with an external stimulus, then the light leakage may be used to provide sensing properties. Changes in the polarization of the light signal input or in the propagation mode, interference effects, or other pertinent optical parameter changes may also be manipulated to obtain a desired effect on, for instance, the sensing functionality of the textile substrate. Alternately, the light leakage from the fiber optics may provide intentional illumination effects to the textile product.
Approaches Using Fiber Optics to Produce Illumination
In some applications, the light-carrying and light-distributing functions of optical fibers are used to provide lighting effects or directed illumination capacity to a fabric.
U.S. Pat. No. 4,234,907, for instance, discloses the use of optical fibers to replace some of the traditional yarns in a woven fabric. The optical fiber surfaces are intentionally scratched so that light can escape from the fibers and provide an overall illumination to the woven fabric. There are many parallel optical fibers in this application, which are necessarily grouped together at their ends to allow light to be coupled into the whole array, thereby illuminating the whole fabric panel. Incorporation of the optical fiber into a woven structure results in the fibers being exposed to crimp, or small radius bends. The optical fiber is incorporated either in the warp direction or the fill direction. In the fill direction, a special machine is used that leaves fiber optic “tails” on only one selvage.
U.S. Pat. No. 4,652,981 takes advantage of the light-carrying capability of optical fibers to create an illuminated belt. In this application, the optical fibers are not integrated into a textile but loosely bundled into a tube.
U.S. Pat. No. 4,727,603 describes feeding multiple side-emitting optical fibers through a fabric and attaching them to an aesthetic side of the fabric for lighted aesthetics on that surface. The fibers are bundled on the non-aesthetic side of the fabric to introduce the light into them. This manner of incorporating optical fibers typically is a more labor-intensive way to distribute fiber optics on a surface, because the fibers were added to the textile after the textile was manufactured, rather than being integrated during fabric formation.
U.S. Pat. No. 4,875,144 is a variation of the '603 patent, in which the optical fibers are grouped into bundles so that different colors of light can be transmitted into different bundles. U.S. Pat. No. 6,217,188 is another variant of the previous approaches, which uses color-changeable light-emitting diodes and a brightness control to produce a more eye-catching visual display featuring the fiber optics. In U.S. Pat. No. 5,424,922, a similar construction is applied to create illuminated safety apparel. In U.S. Pat. No. 5,722,757, a light emitting diode and a non-uniformly side-emitting optical fiber are incorporated onto a soft object to provide illumination to, for instance, a shoe.
U.S. Pat. No. 4,754,372 discloses a floor or wall covering composite with a fibrous face from which the optical fibers project to provide lighting effects. In this approach, multiple parallel optical fibers are grouped to bundle light into them. The optical fibers are incorporated into a composite structure but the fibers themselves are not integral in any single textile component. U.S. Pat. No. 6,709,142 discloses a glove with optical fiber ribbons disposed between an inner and outer layer of the glove, such that light can leak out from the glove to provide illumination for the user.
Approaches using Fiber Optics as Sensor Components
In other textile applications, manufacturers took advantage of the sensitivity of the optical fiber to its state of mechanical flexure, twist, elongation, breakage, or the chemical state in which the fiber exists and the accompanying optical index of refraction changes of the fiber optical system (which result in changes in how the light propagates through the optical fiber).
For example, in U.S. Pat. No. 5,567,932, multiple parallel optical fibers are incorporated into a waste containment geo-membrane. They are described as being laminated into the structure or integral to the textile. They are incorporated in parallel in the longitudinal direction. The optical fibers are bundled to input light. Transmission of light through the optical fibers is monitored to look for breaches, slope creep, subsidence, leachate levels, fires, and types of material present and leaking from the site. The patent does not provide details as to how the fiber is incorporated into the textile. Laying the optical fiber into the composite involves additional processes and labor compared with incorporating it directly into the textile.
In U.S. Pat. No. 6,145,551, a woven product is disclosed that incorporates optical fibers as data transmission lines or sensing lines. U.S. Pat. No. 6,381,482 further broadens this concept to include tubular, flat woven, or knitted products with incorporated optical and electrical fibers for sensing. The fabric must be comfortable as well as functional, since it is to be worn close to a person's skin for monitoring their vital signs. U.S. Pat. No. 6,687,523 discloses using the above article with a means for communicating to an external device, and a means for ensuring a snug fit, to make a garment to monitor the vital signs of an infant (for instance, to prevent sudden infant death syndrome). These textiles, which are designed to be comfortable and durable for use in apparel, are also highly constructed.
Another example of a wearable textile with integrated optical fibers is disclosed in U.S. Pat. No. 6,727,197. The optical fiber is used in a data or power transmission cable that is woven, knitted, or braided. The fabric is easy to manufacture, washable, corrosion resistant, and has high fatigue strength. Because the fabric is designed to be worn, it also has a very full-faced textile construction typical of apparel fabrics.
In U.S. Pat. No. 6,299,104, a set of optical fibers is attached to a parachute, along with light sources and detectors, for monitoring the loads exerted on a parachute during deployment. The optical fiber detection system is attached to the parachute after it is created and, therefore, it is not integral to the textile. Additionally, there are significant labor issues involved in putting the system together.
In US Published Patent Application 2004/0240776A1, the use of optical fibers in a textile for a seat occupation sensor is disclosed. The optical fiber-based sensor detects microbends or modifications of the Bragg wavelength caused by loads positioned on the seat. The optical fiber can be woven into the cover of the seat or into the cushion.
Hence, there have been many textile-based products that utilize optical fibers integrated into the textile, attached to the textile, or incorporated into a composite with a textile for lighting or sensing. However, the articles disclosed use multiple parallel optical fibers and do not include a single optical fiber disposed in a sinuous manner along the textile. Use of a single fiber that is distributed over the whole width and/or length of the textile article can simplify an optical circuit, such as is necessary for a sensing or light-emitting device, since only a single light source and, optionally, a single detector are needed.
Further, having the optical fiber directly integrated into the textile structure allows ease of incorporation of the associated textile into composites, for instance, and insures repeatable placement of the optical fiber. Many of the existing articles described above require post-production attachment of the optical fiber system into the article (that is, the fiber optics are secured to the textile after the textile is manufactured). The present disclosure provides a fiber optic fabric, in which the optical fibers are integrated into the fabric construction.
In a few instances, the optical fiber is directly incorporated into a woven, knit, or braided fabric to produce a fabric with high durability to abrasion, flex, washing, and the like. In these embodiments, a high degree of small radius bends, or crimp, may be imparted to the optical fiber during fabric production, resulting in substantial inability to transmit light without loss. In applications where the optical fiber path is very long, this light loss due to optical fiber crimp may be unacceptable. The present disclosure addresses this problem by providing a family of scrim fabrics, where an optical fiber is integrated in a manner substantially free of small radius bends. Optionally, a continuous length of a single fiber can be extended throughout the fabric.
Because the economics of optical fiber typically dictates sparing use of the fiber, a textile utilizing an optical fiber as a component may preferably be embodied as an open construction, such as a scrim, where there is substantial open space between adjacent yarns. The present disclosure provides a variety of scrim fabrics in which an optical fiber is integrated. Due to its open construction, such an article may be more easily incorporated into a variety of composites including resin impregnated composites (thermosetting or thermoplastic), textile composites, cementitious composites, laminates with various flexible, rigid, and semi-rigid substrates such as wood, metal sheets, foils, multi-ply lay ups, and the like. It is to be understood that there is no requirement that the composite itself have an open construction, rather only that the scrim fabric have such a construction.
Other objects and advantages of the present approach are described herein.